This invention relates generally to a nuclear pumped laser and more particularly to a laser which is pumped by a toroidal fusion reactor.
There is considerable interest in obtaining long pulse, high powered laser radiation at wavelengths that can propagate in the atmosphere, ranging from the near ultra-violet to the mid-infrared (approximately 0.2 to 2 .mu.m. Lasers with a power greater than 0.1 megawatts may be useful in high resolution laser radar, communications with submarines and imaging of underwater environments. Lasers with power exceeding 10 megawatts may be useful for illuminating large remote areas, for drilling tunnels and possibly clearing airport fog. The power requirement of a laser for power transmission to satellites is in the range of from 1 to 100 megawatts. Another application for high powered lasers is in the launching of space vehicles where power in excess of 1 gigawatt per ton orbited is needed with a specific impulse of about 1000 seconds. Presently, there are several approaches for producing a high powered, long pulse laser radiation at wave lengths of less than 2 microns. Examples of devices for producing such radiation are chemical lasers, free electron lasers and nuclear pumped lasers.
Of particular interest to the present invention are nuclear pumped lasers. A substantial amount of work has been performed on developing lasers which are pumped by fission reactors. Examples of which are disclosed in U.S. Pat. Nos. 4,300,106, issued to Robert A. Frosch, which discusses a multiple path nuclear pumped laser; 4,398,294, issued to Thomas G. Miller, which discusses a high power nuclear photon pumped laser; 4,160,956, issued to Walter Fader, which discloses a nuclear pumped uranyl salt laser; 4,110,703, issued to James C. Fletcher, which discusses a .sup.3 He pumped laser; and 4,091,336, issued to George H. Miley, which discloses a direct nuclear pumped laser. All of these inventions use energetic neutrons or fission products from a fission reactor to directly or indirectly pump a laser. Specifically, there has been considerable experimental work done in pumping lasers with fission reactor neutrons via the .sup.3 He(n,p)T reaction, as disclosed by George H. Miley in "Review of Nuclear Pumped Lasers", Laser Interact. and Relat. Plasma Phenom., 6, 47 (1984); M. A. Prelas et al. in "A Review of the Utilization of Energetic Ions For the Production of Excited Atomic and Molecular States", Prog. and Nucl. Energy, 8, 35 (1981); and F. P. Boody et al. "Progress in Nuclear Pumped Lasers" Radiation Energy Conversation and Space, 379, (1978).
The use of controlled fusion devices for laser pumping has been proposed conceptually by George H. Miley in Fusion Energy Conversion and in Trans. Am. Nucl. Soc. 15, 633 (1972) by the same author. U.S. Pat. No. 3,952,263, issued to David McArthur, also generally proposes the concept of using a fusion reactor for laser pumping. However, to date, a scheme for harnessing the power of a fusion reactor and converting such power to useful laser radiation has not been developed.
A fusion reactor pumped laser would have several advantages over a fission reactor pumped laser. First, in a fusion reactor one neutron is available per 17.6 MeV, so that the system can be approximately 10 times more energetically favorable than a fission reactor. In a fission reactor, at most, one neutron can be made available per fission event (190 MeV) to react with the neutron converter.
Second, practically all the neutrons can be made to emerge from a fusion reactor, either by direct streaming or indirectly by reflection from neutron reflective surfaces. Thus, unlike a fission reactor, the laser cells and optical systems need not be installed in the reactor core itself in order to utilize all the free neutrons. From a safety and design viewpoint, it is desireable to decouple the reactor and the laser. Absorption or reflection of the neutrons in a fusion reactor has absolutely no effect on the fusion source.
Third, if .sup.3 He or some other gas is used for neutron conversion, the huge absorption cross section of neutron converter would require that excess reactivity be added to the fission system. This excess reactivity could cause a dangerous power excursion in the event of an escape of .sup.3 He or other neutron absorbing gas.
Fourth, a fusion reactor can have repetitive multigigawatt power rampups with no danger of fuel melting.
Therefore, in view of the above it is an object of the present invention to provide an arrangement for a nuclear pumped laser capable of realizing high laser power.
It is another object of the present invention to provide an arrangement for a nuclear pumped laser capable of realizing high laser power for long pulse lengths (1 second to 1000 seconds).
It is another object of the present invention to provide an arrangement for a nuclear pumped laser with a high electrical efficiency.
It is still another object of the present invention to provide an arrangement for a nuclear pumped laser which utilizes a fusion reactor as a neutron source.
Additional objects, advantages and novel features of the invention will be set forth in part, in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the claims.